Global Positioning System Reference
In-Depth Information
8.6 Standards
8.6.1 Markup Languages
Before looking at mapping, it is necessary to discuss aspects the World Wide Web
and the way it is developing. When the Web emerged it was founded on several
standards, two of which were the brainchild of Sir Tim Berners-Lee. Like all
Internet applications, by definition the use of Transfer Control Protocol over
Internet Protocol (TCP/IP) was needed to move packets of data from computer to
computer reliably. To transfer files File Transfer Protocol (FTP) is used (and at its
heart, each page and media entity of the Web is a file). The inspiration was to
invent the Hyper-Text Transfer Protocol (HTTP) so that users could automatically
fetch new pages (i.e., files) from servers where they are stored by “clicking” on
URLs displayed on the browser application. Behind the scenes, in the script for
the page the URL is spelled out in detail as the Internet address for the file. The
second invention was the language for the scripts known as Hyper-Text Markup
Language (HTML). HTML was extended into a powerful language capable of
displaying information and allowing easy interaction with users via simple mouse
controls. The main problem though was that an HTML script “knows nothing”
about its own content other than how to display it. For example, it showed that a
line of text was in italics but not that the text in question was a postal code,
latitude, or longitude. If the HTML behind a Web page was about geographic
information, the browser, server, or any other computer really could not tell. What
was needed was something like HTML that could tag content to show what it
meant (in human terms) so that computers could do something specific with it (in
computer terms).
The next leap forward (and at the heart of Web 2.0) was the standardization
of the Extensible Markup Language (XML). XML coexists with HTML so that
browsers can interpret both (i.e., HTML was extended in its scope).
XML is a framework to define other markup languages that are domain-
specific. XML is not about geography (or anything else) but it can be used to
specify geographical things like a road, a point of interest, or a set of coordinates
that make up a shape in a way that is meaningful to both humans and machines
(i.e., the script can be read as it is written in plain text and parsed [or encoded on
the fly] by machine software into a database). XML is used to define meaningful
classes of “objects” and then to set real-world instances of the objects to actual
values. (This approach draws heavily on the methodology of object-oriented
computer programming, where abstractions are made about the raw data used by
the machine, in order to make them more meaningful to humans).
 
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